Different manufacturing methods are known for making lined (e.g. insulated) waterproof footwear (e.g. winter boots). These include the conventional lasted process, a process for injection molding the main boot and then inserting into it a loose insulating liner, and, for rubber boots, a vulcanization process applied to a lining layer. Each of these known methods involves numerous separate steps which increases costs and impedes efficiency.
The lasted process is an old, well-known method which uses a last having the shape of the intended boot, the last being a three dimensional model for the intended boot. By this method, the boot materials are formed and fitted onto the last. Hiking boots are typically made in this manner. The selected materials, which may be leather and/or fabrics, including material for a lining layer, are cut into pieces using the last as a model, assembled with a waterproof membrane layer, for example a Gore-Tex membrane, sewn together and then cemented to a rubber sole.
The vulcanization process is also a well-known method for making rubber boots and uses a last. By this method, a lining material is formed to fit over a last and positioned to cover the last. Unvulcanized (i.e. raw) rubber is cut into pieces according to a pattern and the pieces are laid over and cemented to the lining material covering the last. After the positioning of the pieces has been completed, the assembly is put into a heated oven and subjected to heavy pressure which causes the raw rubber to vulcanize and adhere to the insulating microcellular lining.
These known methods involve many separate steps or entail multiple sub-processes which increase production costs. Therefore, a simpler method would constitute a desirable improvement.